You’ve read the piece known as Sexuality and Solitude by Foucault (DE 295) which begins:

In a work consecrated to the moral treatment of madness and published in 1840, a French psychiatrist, Louren*, tells of the manner in which he treated one of his patients – treated and of course, as you may imagine, cured. One morning he placed Mr A., his patient, in a shower-room. He makes him recount in detail his delirium. ‘But all that,’ said the doctor, ‘is nothing but madness. Promise me not to believe in it any more.’ The patient hesitates, then promises. ‘That is not enough,’ replies the doctor. ‘You have already made me similar promises and you haven’t kept them,’ And he turns on the cold shower above the patient’s head. ‘Yes, yes! I am mad!’ the patient cries. The shower is turned off; the interrogation is resumed. ‘Yes. I recognise that I am mad,’ the patient repeats. ‘But,’ he adds, ‘I recognise it because you are forcing me to do so.’ Another shower. ‘Well, well,’ says Mr A., ‘I admit it. I am mad, and all that was nothing but madness.’

*See footnote a in Ethics: subjectivity and truth, edited by P. Rabinow.

This text has appeared in various forms (the one in J. Carrette’s Religion and culture is the best since it is a variorum) but as far as I know the complementary piece by novelist and author Richard Sennett, originally published alongside Foucault in the London Review of Books in May 1981, has not appeared.

With the reorganisation of the LRB website recently in honor of their 30th anniversary, this text is now very easy to read (sub. req’d).

An extract:

A few years ago, Michel Foucault and I discovered we were interested in the same problem, in very different periods of history. The problem is why sexuality has become so important to people as a definition of themselves. Sex is as basic as eating or sleeping, to be sure, but it is treated in modern society as something more. It is the medium through which people seek to define their personalities, their tastes. Above all, sexuality is the means by which people seek to be conscious of themselves. It is that relationship between self-consciousness, or subjectivity, and sexuality that we want to explore. Few people today would subscribe to Brillat-Savarin’s ‘Tell me what you eat, and I will tell you who you are,’ but a translation of this dictum to the field of sex does command assent: know how you love, and you will know who you are.

Michel Foucault and I are working, as I say, on two very different historical periods in which this theme of self-consciousness via sexuality appears. He focuses on how Christianity in its early phases, from the third to the sixth century, assigned a new value to sexuality, and redefined sexuality itself. I focus on the late 18th and 19th centuries, and within that period on how medical doctors, educators and judges took a new interest in sexuality.

There is also a letter, a few issues later in 1981 from a certain William Milne, identified as a professor at Newcastle Upon Tyne who says:

Michel Foucault sternly claims that he is not a structuralist. If this is the case, can he please explain to a layman what he means exactly by ‘technologies of the self’? And why no citations from women themselves? And why no analysis of sado-masochism? Nietzsche’s aphorism, ‘Thou goest to woman? Do not forget thy whip,’ tells us more about recent history surely than the theories of Tissot and Boerhaave, or, come to that, the obsessively self-centred memoirs of Casanova, ever can.

Sennett then offers a final series of remarks centering around Tissot’s Onania (1758):

Tissot set in motion three attitudes about auto-eroticism that profoundly influenced medical and educational opinion later in the 18th and throughout the 19th century: sexuality in solitude is, first, profoundly arousing; auto-eroticism is, secondly, the condition in which a person is most aware of him or herself. To be both sexually aroused and self-aware, alone, is, thirdly, dangerous: the body is on the road to madness and the soul on the road to perdition. What is important about Tissot’s legacy, and about the phenomenon of auto-eroticism generally in the 19th century, is that through the prism of auto-eroticism authorities attempted to understand eroticism itself. Armed with these three assumptions, researchers set out to try and understand sexuality. Rather than considering people making love together as constituting a domain of knowledge about which the doctor would learn, the notion was to separate the individual and to study him by himself, because it was in isolation that the person felt his sexuality most strongly. It was an application to the study of sex of other forms of 19th-century individualism, this assumption that a person was to be considered as an isolated individual.